Ship-propulsion system



July 10, 1923. 1,461,576 F. H. CLQUGH SHIP PROPULSION SYSTEM Filed Jan. 29 1921 Inventor":

Fredri c Horton Clough,

135 His flttorne Patented July 10,1921 3.

UNITED STATES PATENT OFFICE.

IBEDBIC H. CLOUGE, OF HILLMORTON, HEAR RUGBY, ENGLAND, ASSIGNOB '10 GEN- ERAL ELECTRIC COMPANY, A COBFQBATIGN 0]? NEW YQRK.

SHIP-PLEZGPULSIGH SYSTEM.

Annlieelion To all wilom may concern:

Be it known. that l, Fmrnnro @LOUGH, a subject of the King 01 Britein, residing eb Hillcrest, Hilim A, near Rugby, in the county of erriiclrshire, England, have invented certain new end useful lmprovemenis in Ship-Propulsion Systems, of which the following is a specification.

My invention relates to power s s'eins wherein an adjustable speed genera sor of the synchronous type is arranged to supply energy to e WOI'k motor, and is particularly adapted to systems in which the loedon the motor varies at a comparatively slow rate as in electric ship propulsion systems. An oioject of my invention is to provide improved means for controlling the excitation of such systems in accordance with the requirements of she load.

I shall describe. one embodiment of my invention in which means are provided for regulating the excitation of an alternating current generator, although it will be obvious to those skilled in the art that -e invention can equally well be a plied to elrernating current motor. ccording to my invention the generator or motor is given .n characteristic similar to that". obtained from a compound wound direct current gem ereior or motor.

My invention will loe better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the eppended cla'ms.

ln tile singl figure of the accompanying drawing, e prime mover, which will preferably be an elastic-fluid turbine, is 1 e sented at 1. This lurbine will be prov with any suitableform of governor may be adjusted to liold the turbine desired speed. The prime mover is di I rectly connected to an elternelzing cur-rent dynamo electric machine 2 of the syncleronous type, connected through mains 8, in manner well lmown in the art, so the motor 3 which is dire y connected to the we Dlish this resull.

iclr

ent is suppl e gen eraser A eole source oi direci current sented by the 6. The exciting c flows from ni ins 6 to the slip rir oi the generator 'Qnrcugii en adjustaol sistance 8 which represents any suitable means for controlling the generator field strength. is is obvious to those skilled one ii is immaterial to my invention whether ilie field strength regulelor operates 15o control directly the current in the generator field Winding or [to control said current indirectly by seizing e suitable exciier vvnicli supplies vhe field current, According to my invention the Field s'sreng ifn regulating means is controlled in 39 eccoreence with the current sugolied from the generator 2 to "He motor so accome regulating means is operated by e torque motor 9 operating against an adjustable counter-torque device represented as a spiral spring. The

'36 in motor 9 is preferably of the series coinrnutaeor type, either single or polypliase, and this motor should he designed to have. a large torque and smell moment of inertia. so that ii will lie able to start and shoe quickly. In the drawing this motor is recresented as e 'llireephase series commutator w" tor supplied one the current "trans- Eorrners 11 which furnish a current to the torque inoior proporlzional to the current the resins 3. The motor 9 is connected drive the 12 in any desired manner, susble gearing" 33E being represented in the drawing. When current flows through the w tor 9, it will send to rotase in such is way sna l", the exci'levion oi the general: 1 increased 2 -d this iendency lo rotatic' ed by lire spring 10. The one force of bile motor and spring siren relatively "no ll'iQ friction oi n18 device r lend wheel or equivalent means 14 is preferably provided secured to the incest-oi; arm 12 and, es indiceied in one means are provided whereby the means meg; l3e

hand wheel independently of the torque motor 9. To accomplish this purpose arm 12 and hand wheel 14 may be secured to a member 15, slidable on shaft 16 which is driven by the motor 9. A slot is provided in the member 15 and a spring 18 is arranged to hold member 15 normally in engagement with a pin 17 secured to the shaft 16. By pressing he hand wheel 14 inwardly, the arm 12 maybe disengaged from the automatic drivin mechanism and may be rotated by han so as 'to give any desired value of excitation. When the hand wheel 14 is released, the spring 18 re-establishes drivingconnection between the regulating means and the torque motor 9. By this'means the excitation can be varied at will so that any desired voltage can be obtained from the alternator under any given condition of load or when no current is flowing.

The control spring 10 can be adjusted by the adjusting means 19 so as to regulate the automatic compounding efiect due to the main current.

The operation of the system illustrated in the drawing will be obvious to those skilled in the art from the preceding description. With any given speed of the generator an increase of load upon the propeller driving motor produces an increase of current in the mains 3. Current transformers 11, therefore, supply increased current to the torque motor 9 which operates the-regulating means to increase the generator field strength. Variations in load on the propeller at any given speed of the generator may be due to head winds or other causes. The pitching of the ship produces variations in load on the propeller driving motor due to the propeller coming out of the water in a heavy ,sea. These pitching movements have a period of about seven seconds andthe apparatus operates sufiiciently rapidly to ad ust the alternator voltage in accordance with such load variations. In an electrically (propelled ship the speed of the ship is varie by controlling the speed and frequency of the generator, and it is desirable that the voltage of the generator rise with increased speed for the reason that the load on the propeller motor increases rapidly with increase in speed. A commutator motor of the type shown gives a torque depending upon the current passing through 1t: more or less independent of the fre- 'quency of the system from which such current is obtained. Selection of this type of motor, therefore, simplifies the eontrollin apparatus for the reason that no specia provision need be made for compensating for changes in frequency. In order to adjust the voltage held by the automatic regulatin means, the spring 10 may be adjusted an at any desired moment the operator may manually assume control of the regulating device by releasing the engagement between the regulating means and the torque motora With my automatic regulating arrangement, it is apparent that the generator excitation is strongly increased during .manoeuvring operations, since during such 0 ration the motor takes a heavy current. he motor is thus prevented from falling out of step when the load is heavy, and the efiiciency and capacity of the plant are increased by reason of the reduced heating of the generator field winding during operations at light load.

Where the motor is of the synchronous type, it is obvious to those skilled in the art that it is possible to apply the exciter regulating means to the motor field winding since the maximum torque of the motor may then be adjusted by controlling the excitation of either the generator or the motor.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. An electric ship propulsion system comprising an adjustable 'speed prime mover, a synchronous generator riven thereby, an alternating current propeller driving motor connected to be supplied by said generator, means for regulating the field strength of said generator, and means for operating said regulating means comprising a series commutator type torque motor connected to exert a torque proportional to the current supplied to the motor.

2. An electric ship propulsion system comprising an adjustable speed prime mover, a synchronous generator driven thereby, an alternating current propeller driving motor connected to be supplied by said generator, a variable resistance for regulating the field strength of said generator, a series commutator type motor connected to operate said variable resistance, an adjustable torque device for opposing rotation of said motor, and current transformers connected to supply said commutav tor motor with current varying with the currentsupplied to said propeller driving motor.

3. An electric power system comprising a variable voltage variable frequency dynamo electric generating machine ofthe synchronous type and an alternating current load driving dynamo electric machine, means for regulating the field strength of one of said dynamo electric machines, and means for operating said regulating means comprising a series commutator type torque motor connected to exert a torque varying with the current supplied to the load driving dynamo electric machine.

4.. An electric ship propulsion system comprising a variable voltage variable frequency generator, an alternating current propeller driving motor supplied thereb a Y b re i t n e for reg lati g he fieti tor, and means where y said resistance may be adjusted independently of the torque motor.

In witness whereof, I have hereunto set my hand this first day of January, 1921. FRED. H. CLOUGH. Witnesses:

J. A. Fos'mn, D. WHITE. 

